Engines, for example IC engines burning gasoline, diesel or biofuel, output various substances which must be treated to meet current and future emissions legislation. Most commonly those substances comprise hydrocarbons (HC), carbon monoxides (CO), mono-nitrogen oxides (NOx) and particulate matter, such as carbon (C), a constituent of soot. Some of those substances may be reduced by careful control of the operating conditions of the engine, but usually it is necessary to provide an emissions cleaning module downstream of the engine to treat at least some of those substances entrained in the exhaust gas. Various apparatus for reducing and/or eliminating constituents in emissions are known. For example, it is known to provide an oxidation device, such as a diesel oxidation catalyst, to reduce or to eliminate hydrocarbons (HC) and/or carbon monoxide (CO). Oxidation devices generally include a catalyst to convert those substances into carbon dioxide and water, which are significantly less harmful. As a further example, emissions cleaning modules may include filtration devices to restrict the particulates present in the exhaust gas from being output to atmosphere. The soot collected in the filtration device must later be removed to maintain the efficiency of the filtration device. The methods by which soot may be removed from the filtration device are well known in the art and may generally be referred to as regeneration which occurs at elevated temperatures. In addition, it is known to reduce or eliminate mono-nitrogen oxides (NOx) in diesel combustion emissions by conversion to diatomic nitrogen (N2) and water (H2O) by catalytic reaction with chemicals such as ammonia (NH3) entrained in the exhaust gas. Generally ammonia is not present in exhaust gas and must therefore be introduced upstream of a catalyst, typically by injecting a urea solution into the exhaust gas which decomposes into ammonia at sufficiently high temperatures.
By these methods, engine emissions can be cleaned, meaning that a proportion of the harmful substances which would otherwise be released to atmosphere are instead converted to carbon dioxide (CO2), nitrogen (N2) and water (H2O).
Against this background there is provided an emissions cleaning module for a diesel engine.